Grinding machines



Oct. 23, 1956 ,A. KRAUSE ET AL GRINDING MACHINES s She e-t s-Sheet 1 Filed May 25, 1954 kmm llrlllllllll Irwentbmx vilqgmijl.-E awse,

Oct. 23, 1956 A. KRAUSE ET AL 2,767,521

GRINDING MACHINES Filed May 25, 1954 5 Sheets-Sheet 2 as w 4 Q r? m "m, y

N liwentors J1 I. Kflazwe, v Geo e filevesgue,

by WW 113202 1 9 Get. 23, 1956 A. L. KRAusE ET AL 2,767,521

' GRINDING MACHINES I Fi].ed May 25, 1954' 5 Sheets-Sheet 3 Oct. 23, 1956 A. L. KRAUSE ET AL GRINDING MACHINES 5 Sheets-Sheet 4 Filed May 25, 1954 muowmsn LIMITSWITCR I l l l I Oct. 23, 1956 A. L. KRAUSE ET AL 2,757,521

' GRINDING MACHINES Filed May 25, 1954 v 5 Sheets-Sheet 5 29.62 I A '2 7' ml 10 munwusa.

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United States Patent Office 2,767,521 Eatented Get. 23, 1956 2,767,521 GRINDING MACHINES Application May 25, 1954, Serial 432,188 11 Claims. (Cl. 51-95 The present invention relates to improvements in grinding machines and more particularlyjto an improved device for finish grinding a work piece to size.

In grinding machines and more particularly plain grinding machines which are equipped witha spark timing device including means acting automatically upon'completion of the sparking out period to relatively separate the grinding wheel and the work it has been found that there is a tendency for the grinding wheel 'tomark the work.

In machines of the general type herein disclosed having a reciprocating work table and with support and rotating devices carried on the table and a cross slide on which the grinding wheel is moved against and away from the rotating work piece, a spark timing arrangement isnormally provided which is rendered operative as the grinding wheelreaches the limit of its depth feeding movement and acts upon completion of a sparking out period to cause the grinding wheel to be rapidly withdrawn from the work. The spark timing arrangement may, for example, be electrically operated including a, limit switch which at the extreme cross feed infeed starts the spark timing by actuating a time delay relay. When this relay drops out an electric motor is energized to effect the rapid travel of the wheel slide in a reverse direction away from the grinding wheel. Heretofore, it has been found impossible to avoid a slight nudging of the work bythe grinding wheel with the resulting objectionable marking of' the work as'the grinding wheel starts its rearward movement. It is a principal object of the invention to provide in machines of the general type described a device for more accurately controlling the relative positioning movements of the grinding wheel and work at the limit of the grinding wheel infeed and the withdrawalof the'grindin g wh'eel upon completion of a grinding operation to' produc'e on the work piece a finish of desired quality.

With this and other objects in view as may hereinafter appear a principal feature of the invention consists .in the provision of a vibrating means in the machine which will act during the sparking out period,'and as the grinding wheel is moved away'from the work to average and thereby to iron out any hard spots or inaccuraciesin the operation of the devices for positioning and relatively retracting the grinding wheel and work.

Another feature of the invention consists in theprovision of spring means for biasing the grinding wheel" and its supporting carriage continuously away from the work toward a retracted position so that when the vibrator device is in operation during and immediatelyf ollowing the sparking out operation there is a tendency at all times for the grinding wheel and carriage to be drawn rearwardly, thusovercorning any tendency of the grinding 'wheel "to be thrust forward at the start of the rapid movement withdrawal with the grinding wheel. i

With the above noted and other objects in view may hereinafter appear, the invention consists also in the devices, combinations and arrangements'of parts hereinafter s-l ne described and claimed, which together with the advantages to be obtained thereby will be readily understood by'on'e skilled in the art from the following description taken in connection with the accompanying drawings, in which V Fig. 1 is a view .in front elevation of a grinding machine embodying the several features of the invention;

Fig. 2 is a view in left side elevation of the machine;

'Fig. 3 is a sectional view in right side elevation illustrating particularly the cross feed slide shown in Fig. 2 and the rapid tranverse and cross feed mechanism associated therewith;

' Fig. '4 is a detailed sectional view of the three-phase motor brake associated with the cross feed rapid traverse motor;

' Fig. 5 is a wiring diagram illustrating a portion of the electrical connections for the machine;

Fig. 6 is an explanatory diagram of the direct current control circuit of the' machine; and

Fig. 7 "isan explanatory diagram of the electrical connections for certain of the electrical units. The grinding machine illustrated in the drawings as embodying in the preferred form the several features of thejinvention comprises a base 112, a longitudinal movable work supporting table 114 which is arranged to slide in ways "116 on the base, a headstock bracket 118 adjustably secured on the table, a footstock 120 also secured on the table, and a grinding wheel carriage 122 which is supported on cross ways, not specifically shown, mounted on the base. a i

The grinding machine shown is, except as hereinafter more fully set forth, similar to the machine fully shown and' describe-d in the U. 'S. patent to Mathewson and Krause, No. 2,165,898, patented July 11, 1939, for Grinding Machines, and will herein be described only so far as believed necessary to illustrate the connection of the invention; therewith. The illustrated machine is provided with conventional power means for operating the several support including a main d riving motor which acts through mechanical driving connections, not specifically shown, to drive the work table. A headstock motor 132 carried on the headstock bracketlls is connected through suitable reduction gea rconnections to drive the headstock spindle, generally indicated'at 134.

The grinding wheel carriage 122 provides support for a grinding'wheel 136 and a grinding wheel support shaft 138 which is continuously driven by means of a grinding wheel motor 140 mounted on the grinding wheel carriage I22. l

' The cross feed mechanism of the present machine for advancing and retracting the wheel spindle carriage, as best shown in Fig. 3, comprises a cross feed nut 144 rigidly secured to the underside of the grinding wheel carriage 122 and a cooperating feed screw shaft 146 which is supported on the machine frame for rotational feeding movement and for axial movement to impart a rapid movement to the grinding wheel carriage toward and away from the work as hereinafter to be more fully described. Rotational movements are imparted to the feed screw to advance and retract the carriage by means of a gear 143 which is splined onto the feed screw shaft 146 to rotate therewith and is held against axial movement between the two halves of a bearing support 150 within which the feed screw shaftis mounted for rotational and axial movement. Meshing with the gear 148 is a pinion 152 formed on the end of a shaft 154 which at its forwar'd end carries the cross feed handwheel 156 shown in Figs. 1 and 2. A collar 158 secured to the feed screw shaft 146 provides a positive stop to limit the advancing movement of the nut 144 and carriage with relation to the feed screw. A flange 160 formed on the feed screw similarly provides a positive stop to limit the retracting movement of the nut 144 and carriage with relation to the feed screw.

Cross feeding movements are imparted to the grinding wheel carriage by rotation of the cross feed handwheel and associated cross feed shaft 154 either manually or by power operation of a cross feed ratchet 162 and pawl 164, as generally indicated in Fig. 1. In operation the cross feed handwheel is set angularly with relation to the cross feed shaft 154 so that in the limit position shown the grinding wheel has been moved to its finished depth feed position, and in which the pawl 164 has been rendered inoperative by engagement with a shield 165. The handwheel is then moved in a clockwise direction away from the limit position to back off the grinding wheel prior to the start of the grinding operation. Movement of the cross feed handwheel in a counterclockwise direction to the limit position shown in Fig. 1 thus causes the grinding wheel to be advanced to its finished depth feed position.

The illustrated machine is also provided with a cross feeding rapid movement mechanism for imparting a rapid movement to the grinding wheel carriage toward and away from the work. With the construction herein disclosed, the rapid movement of the grinding wheel is effected by means of mechanism including a wheel slide rapid movement lever which operates to shift the feed screw 146 axially between two exactly determined positions. As best shown in Fig. 3, the shifting mechanism comprises a crank shaft 168 having formed thereon a crank pin 170 offset from the shaft which is connected by means of a short link 172 and connecting pin 173 to the downwardly extending arm of a crank actuated shift lever 174 carried on a pivot shaft 176. The upper end of the shift lever 174 takes the form of a yoke which carries two rolls 178 arranged to engage in a peripheral groove 180 formed on a sleeve member 182 by means of two sleeve cushioning members 184 which abut respectively against a rib 200 and a collar 204 on the sleeve member 182 to provide a movable connection between the shift lever 174 and the sleeve 182. In order to permit the feed screw to turn freely with relation to the supporting sleeve member 182 and at the same time to prevent a relative axial movement thereof, the sleeve member 182 carries on the internal periphery thereof bushings 186 and 188 to receive the feed screw shaft, and is prevented from axial movement with relation to the screw shaft 146 by means of end thrust bearings which are supported respectively against the flange 160 and a nut 190 screw threaded to one end of the feed screw shaft. The assembly including the feed screw 146 and sleeve 182 are externally supported in two bearings 192, 194 formed in opposite ends of a casing 196 within which the entire mechanism for axially shifting the feed screw is housed. A key 198 supported within the bearing 192, as shown in dotted lines in Fig. 3 engages in a corresponding keyway or slot in the periphery of the sleeve 182 to prevent rotational movement of the sleeve. The movement of the feed screw shaft 146 and sleeve 182 in a forward direction is limited by the engagement of a flange or rib 200 on the sleeve 182 with a stop surface 202 formed on the inner face of the bearing 194. Movement of the feed screw shaft 146 and sleeve 182 in a rearward direction is similarly limited by the engagement of a flange which takes the form of a collar 204 rigidly secured to the sleeve 182 with a corresponding stop surface 206 formed on the inner face of the bearing 194.

The throw of the crank lever 174 is adjusted with relation to the length of travel of the feed screw 146 and sleeve 182 between the two limiting positions above described so that 180 of rotation of the crank shaft 168 will operate to move the feed screw and sleeve 182 from one to the other of said limiting positions with the rib 200 or collar 204 in engagement with the corresponding abutment.

The rotation of the crank shaft 168 is controlled by means of an electric motor 210 through driving connections which include a drive shaft 212 in axial alignment with and keyed to turn with the armature shaft 214 of the motor. A worm 216 on the drive shaft meshes with a worm gear 218 secured to one end of the crank shaft 168. There is also provided with the motor a mechanical multiple disk brake, see Fig. 4, which comprises a brake member 220 splined to the lower end of the armature shaft 214 between a braking surface 222 formed rigidly with the motor case and an axially movable braking member 224 which is supported against turning and is forced yieldably down by means including an adjusting pin223 and a spring 225 seated in a recess in a cover member 226 secured to the wall of the brake housing 229. The brake is normally held in braking position by means of said compression spring unit 225. The movable brake member 224 is moved in an opposite direction to release the brake by means of a three-phase magnetic braking device which may be of ordinary description including the magnet 228 shown which acts when energized to move the brake to its open inoperative position.

For controlling the operation of the cross feed rapid movement, electric connections are provided which can be operated either manually or electrically to start the motor 210 and to release the brake, and to operate thereafter to stop the motor and set the brake, and thus to stop the crank shaft 168 at the end of each successive half revolution of the crank 170.

The cross feed mechanism may be operated in accordance with an automatic cycle of operations which may, for example, be that more particularly described in the Mathewson et al. Patent No. 2,165,898, above referred to.

Starting with the cross feed rapid movement mechanism in its retracted position and with the grinding wheel handwheel backed away from its limit position by an amount which is in excess of the amount of stock to be removed from a work piece, the cross feed rapid movement motor 210 is energized to drive the crank shaft 168 and crank pin 170 through 180 and thereby to advance the grinding wheel carriage to its advance position shown in Fig. 3. The power operation of the cross feed pawl and ratchet mechanism is then started to advance the grinding wheel to the finish depth grinding position in a which the pawl 164 rides onto its shield 165. The grinding wheel carriage is maintained in its fully advanced po sition during a dwell or sparking out period, after which the rapid movement motor 210 is again actuated to rotate the crank shaft 168 and crank pin through a second to effect the rapid withdrawal of the grinding wheel from the work. In the usual automatic cycle of grinding and thereafter separating the grinding wheel from the work a fault has been observed, particularly where work is done to close tolerances and a fine finish is required, in that a mark appears on the work piece at the point at which the cross feed rapid movement mechanism becomes operative to move the grinding wheel away from the work. Up to the present time no satisfactory means have been devised for eliminating such marking of the work. Such marking has been noticed in connection with both plunge cut and ordinary grinding, in which the Work piece is moved longitudinally with relation to the grinding wheel on the table. The cause of this undesirable marking which has been encountered on the grinding machines, particularly in grinding to a fine finish, has not been precisely established, but is believed to result from the release of tensions and strains built up in the mechanism during the advancing of the grinding wheel to its depth position, and more particularly from the further disturbance of the parts of the mechanism as the cross feed rapid movement mechanism be- '3 iier tiv to r tract .the. g inding whee f om the work.

;-In caprying out the .p iflsent ;inyention means v are proyidedforsettingup a yibrationinthe machine which has the effect of causing all .of the parts of the operating mechanism to be freed of any stresses or .tensions, with the ,resnlt that the undesirable marking previously observed at the beginning oftherapidretracting movement has been eliminated.

The vibrator .mechanism is preferably started during the sparkingoubperiod .whenthe grinding wheel has been advanced to -.the finished depth position and the vibration thus set up is continued .until slightlybefore the cross feed rapid motion mechanism is rendered operative to start the retracting movement of the grinding wheel away from the work. The vibrator mechanism has been found tooperate effectively to insure the production of an accurate unmarredfinishon thework under a variety of conditions .which'would normallyhave been considered damaging as, for .example, to .-iron out and to .dissipate the effects of inside influences ,such as reciprocating tables, valves or solenoids, and also outside influences including vibrations set up bypassing trucks or by the operation of other. nearby machines.

In the preferred form of .the invention shown, the

.vibration referred to is produced by connection in a closed circuit of a single phase only of the three-phase rapid movement motor brake so that a rapid vibration of the parts of .the brake results, which vibratory movementis transmitted through the machine and serves to shake out any tensions or tightness in the machine operating mechanisms. I

Further in accordance with the invention means are provided for continuously biasing-the grinding wheel,-its

supporting carriage, and the operating 'connectionsfor the grindingwheel carriage, rearwardly away from the work. It has been found that a spring device which acts continuously to bias the grinding wheel carriage in a rearward direction assists substantially to avoid any marking of the ground work surface when the grinding wheel is retracted from the work. As best shown in Fig. 2, the device employed for biasing the grindingwheel carriage and associated parts away from the work comprises a spring 230 connected at oneend to a pin 231 on the grinding wheel support, and at its other end to a pin 232 on a bracket 233 secured to a rear portion of the machine. Y

The electrical controls-by means of which the automatic operation of the grinding wheel cross feed is effected are particularly shown in Figs. 5, 6, and 7. It

will be understood that only so much of the electrical controls of the machine are shown as believed necessary to illustrate the connection with the present invention therewith. For a full disclosure of theoperating and control devices for the grinding machine shown reference may be had to the disclosure in the patentto Mathewson 2,165,898, above referred to.

The electrical driving units of the machine include several alternating current motors including the main grinding wheel spindle motor 140, the cross feed rapid movement motor 210 and a generator motor 235 which is in turn directly connected to drive a headstock motor generator 236 and a table motor generator 237. The

headstock. generator is a constant potential self-excited generator which supplies the necessary power for running the headstockmotor 132 that also supplies current tothe direct current control circuit hereinafter more particularly referred to, and to the fields of all the direct current -mot ors and generators, herein .mentioned.

In accordance with the present inventionthere is connected into the three-phase circuit with the rapid movement, cross feed motor a handwheel limit switch .and time delay relays forcausing ,theretracting of thegrinding.wheelto be .delayedduring a sparkin out period, and

6 fo causins s pha o the c s ee rapid m ment m o b ak t -be en a da a i a i The electrical devices by means of which the vibrating device above described is rendered operatiue when grinding operation has proceeded to depth comprise a depending cam member 240 on the handwheel 15 6. The cam member acts when the handwheel moving counterclockwise reaches its depth feed limit position to engage with a contact roller 242 on a switch arm 244 which is thus depressed causing a handwheel limit switch 246 to be shifted from its upper to its lower position, as shown in Fig. 7. Movement of the handwheel in the reverse direction in which the grinding wheel is moved away from the work causesthe cam 240 to be disengaged from the contact roller 242 thus permitting the handwheel limit switch 24-6 to be shifted to its alternate raised positionin which contacts 78-101 are closed and contacts 78-104 are open. The electricaldevices referredto also include two timing relays which are energized by movement of thehandwheel switch 246 to its lowered position, including the timing relay T which causes the vibration unit to operate for a limited period upon actuation ofthe handwheel limit switch, and a timing relay T which operates after a limited sparking out period to initiate the rapid movement of the grinding wheel away from the work. ,The electrical connections for setting up a vibratory movement of the cross feed rapid movement brake mechanism comprise a relay coil V and switch connections controlled thereby which cause the cross feed rapid movement motor brake to be single phased with the result that the brakemember 224 vibrates rapidly from one to the other position.

Theoperation of the vibrator device will be described in connection. with a brief review of an automatic cycle .of operations ofthe illustrated machine as follows:

Assuming that the machine is set up in starting position and start button having contacts 83-75 has been pressed, both time coils T and T are energized through the closed contacts 1111-78 of the handwheel limit switch. Contacts T 103-104 in the circuit with relay V are now closed, and contacts T 3-35 in circuit with the relayRC stand open. The contactsmarked V in lines 1&5 and 106 respectively, to the motor 210 are opened to prevent single phasing of the motor 210. P01- lowingthe normal operation of the machine, the end of the cross feeding movement will be reached as determined by the setting of the blank space or shield on the handwheel. At this point the cam 240 engages the contact roller 242 to shift the handwheel limitswitch to its down position opening switch contacts 101-78 and closing switch contacts 104-78. Coils T and T arethus deenergized to start their timing periods. An indicating light 250 goes on indicating the spark out timing period. When the limit switch contacts 104-78 close, coil V is energized. Contacts V 88-105 and V 89-106 close causing a single phase of the three-phase crossfeed rapid movement motor brake to be energized thus setting up a vibratory movement of the brake element 224.

After a fixed timingperiod T 103-104 opens and stops the vibration, subsequently after a predetermined timing period has elapsed the timing coil T runs out releasing contact T 3-35 which closes to energize relay coil RC forming partof the automatic cross fced cycle mechanism. RC contact 25-26 opens so that the F or cross fed forward coil is deenergized. Contact RC 26-27 closes so that grinding wheel slideback coil B The invention having been described what is claimed is:

1. In a grinding machine having a grinding wheel, a grinding wheel support, a work support, and means for imparting relative feeding movements of said supports to an infeed limit position, the combination of a vibratory device mounted in the machine operative to set up a continued vibratory disturbance in portions of the machine including said means for imparting relative feeding movements to said supports, upon movement of said supports to said infeed limit position and thereby to release any tensions existing in said means for impartingrelative feeding movements to said supports.

2. In a grinding machine having a grinding wheel, a grinding wheel support, a work support, and means for imparting relative feeding movements of said supports to an infeed limit position, the combination of a vibratory device mounted in the machine acting when rendered operative for setting up a continued vibratory disturbance in portions of the machine including said means for imparting relative feeding movements to said supports, and control means on the machine for rendering said vibratory device operative and inoperative.

3. In a grinding machine having a grinding wheel, a grinding wheel support, a work support, and means for imparting relative feeding, sparking out, and separating movements to said supports, the combination of a vibratory device mounted in the machine and adapted when rendered operative to set up a continuing vibratory disturbance in portions of the machine including said means for imparting relative feeding, sparking-out and separating movements to said supports, and means actuated from the machine for rendering said vibrating device operative during the sparking out period and thereby to release any tensions in said means for imparting relative feeding, sparking-out, and separating movements to said supports.

4. In a grinding machine having a grinding wheel, a grinding wheel support, a work support, and means for imparting relative feeding, sparking out, and separating movements to said supports, the combination of a vibratory device mounted in the machine and adapted when rendered operative to set up a continuing vibratory disturbance in the machine including said means for imparting relative feeding, sparking-out, and separating movements to said supports, means for operating the machine in accordance with an automatic cycle including a relative feeding movement of the grinding wheel and work to depth, sparking out, and a relative separation of the grinding wheel and work, and means acting in accordance with said automatic cycle for rendering said vibratory device operative during the sparking out period.

5. In a grinding machine having a longitudinally movable work support, a grinding wheel, a transversely movable wheel support, actuating means for the grinding wheel support including slow infeeding means for the grinding wheel support including a cross feed handwheel, a grinding wheel support rapid travel mechanism, control means for effecting a rapid movement of the wheel and the slow infeed of the grinding wheel support, and thereafter a rapid movement of the grinding wheel away from the work, and a vibratory device constructed and arranged in said machine with relation to said actuating means for the grinding wheel support to set up a continuing vibratory disturbance in the machine at the end of said infeed.

6. In a grinding machine having a longitudinally movable work support, a work rotating means mounted on the work support, a grinding wheel, a grinding wheel support arranged for feeding movements toward and away from the work, means including a handwheel for eifecting a slow infeed of the grinding wheel support,

a grinding wheel rapid travel mechanism for effecting an additional rapid movement of the grinding wheel support toward and away from the work, spring means biasing the grinding wheel support continuously away from the work, control means operative upon movement of the grinding wheel to depth to efiect a dwell of the grinding wheel support and thereafter a rapid withdrawal of the grinding wheel support, a device for setting up a continuing vibratory disturbance in portions of the machine including said means for eifecting a slow infeed of the grinding wheel support, and means actuated from the machine for rendering said vibratory device operative during the sparking out period.

7. In a grinding machine having a longitudinally movable work support, and work rotating means carried by said work support, a grinding wheel, a grinding wheel support arranged for transverse feeding movements toward and away from the work support, mechanism acting when rendered operative to advance the grinding wheel support and grinding wheel therewith to efiect a depth grinding cut and thereafter to withdraw the grinding wheel support and grinding wheel, a vibratory device mounted in the machine and adapted when rendered operative to set up a continuing vibratory disturbance in the machine including said mechanism to advance and to withdraw the grinding wheel support and grinding wheel, and thereby to release any tensions in said mechanism, and yieldably acting means continuously biasing the grinding wheel support in one direction with respect to said advancing and retracting mechanism.

8. In a grinding machine having a work support, a grinding wheel and grinding wheel support adapted for feeding and rapid movements toward and away from the work support, actuating connections on the machine for imparting feeding and rapid movements to the grinding wheel support toward and away from the work support, and spring means connected between the machine and the grinding wheel support urging the grinding wheel away from the work, and a vibratory device mounted in the machine and adapted when rendered operative to set up a continuing vibratory disturbance in portions of the machine including said actuating connections to release any tensions in said actuating connections and thereby to maintain a continuing biasing strain on the grinding wheel support and the grinding wheel support actuating mechanism away from the work.

9. In a grinding machine having a longitudinally movable work support, a grinding wheel, a transversely movable wheel support, slow infeeding means for the grinding wheel support including a cross feeding handwheel, a grinding wheel rapid travel mechanism arranged for imparting a rapid movement of predetermined extent to the grinding wheel support toward and away from the work support, a grinding wheel rapid movement electric motor and a three-phase motor brake associated therewith, and means operative at the end of the infeed to set up a single phase circuit through said motor brake and thereby to set up a continuing vibratory disturbance in the machine.

10. In a grinding machine having a base, a longitudinally movable work support carried on the base, a grinding wheel, a transversely movable wheel support carried on the base, slow infeeding means for the grinding wheel support including a cross feed handwheel, a grinding wheel rapid movement mechanism arranged for imparting a rapid movement of predetermined extent to the grinding wheel support toward and away from the work support, a vibratory device supported on the machine and directly connected with said grinding wheel rapid movement mechanism, control means for effecting a rapid movement and thereafter a slow infeed of the grinding wheel support, and thereafter a rapid movement of the grinding wheel support away from the work, and means for actuating said vibratory device to set up a continuing vibratory disturbance through said rapid movement mechanism and through said base at the end of said infeed.

11. In a grinding machine having a longitudinally movable work support, a grinding wheel, a transversely movable wheel support, slow infeediiig means for the grinding wheel support, a grinding wheel rapid movement mechanism for imparting a rapid movement of predetermined extent to the grinding wheel support toward and away from the work support, spring means biasing the grinding wheel support away from the work, a vibratory device connected with said rapid movement mechanism for setting up a continuing vibratory disturbance through said rapid movement mechanism, and means acting when rendered operative to actuate said vibratory device at the end of the infeed.

References Cited in the file of this patent UNITED STATES PATENTS Knowles Feb. 8, 1927 Mathewson July 11, 1939 Comstock Nov. 30, 1954 

